We have solved the crystal structure of an alpha-neurotoxin from sea snake venom at 2.2 A resolution. All of the atoms in the protein have been located and a model has been proposed for binding to the acetylcholine receptor. We are currently refining the structure at 1.38 A resolution and plan to extend the work to include cardiotoxins, longer gamma-neurotoxins, and multi-subunit neurotoxins. Small crystals of some of these have already been obtained. Work on the crystal of thrombin is currently directed towards the solution of the structure by location of the trypsin molecule within the thrombin unit cell, followed by bootstrap refinement. In parallel, efforts are continuing to increase our supply of large crystals, crystallize inhibited thrombin, and obtain more favorable crystal forms. We are also assessing the possible use of rotation/oscillation photography to collect data on smaller crystals of our present form, with a view towards conventional isomorphous replacement structure determination.